1. Field of the Invention
The present invention relates to post-growth processing of sublimation grown crystals and, more particularly, to annealing of sublimation grown crystals, such as SiC crystals.
2. Description of Related Art
Wafers of silicon carbide of 4H and 6H polytypes serve as lattice-matched substrates to grow epitaxial layers of SiC and GaN, which are used for fabrication of SiC- and GaN-based semiconductor devices.
Large SiC single crystals used for semiconductor industrial applications are commonly grown by sublimation using a process called physical vapor transport (PVT).
Unfortunately, boules of crystals grown using this technique are stressed, which leads to cracking. Cracking can happen during cooling of the boule to room temperature, during mechanical separation of the boule from a seed-holder, as well as during subsequent steps of fabrication and polishing.
It would, therefore, be desirable to overcome the above problems and others by providing a method for reducing stress in sublimation grown crystals. Still other benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.